1. Field of the Invention:
The present invention pertains generally to the mitigation of the destructive effects of a major earthquake in a populated area, and specifically to the following applications:
a. to stop the flow of gas to an occupancy where major earthquakes or other shocks above a pre-determined intensity may cause a gas line to rupture, resulting in a life/property threatening fire, and
b. to stop the flow of gas to an occupancy in the case of a sheared gas line within said occupancy from other than a vibratory shock, and
c. to stop the flow of gas from a hazardous material storage container in the event of a vibratory shock above a predetermined intensity, or when an excess flow of gas passes through said valve, or when said container is tilted beyond a pre-determined angle from the vertical.
2. Description of the Prior Art:
Heretofore, devices which shut off the flow of gas to an occupancy have generally been sensitive to only one, and in some instances, two of the effects of a major earthquake; tilting beyond a pre-determined angle from the vertical, lateral shocks above a pre-determined intensity, and from an excess velocity of gas through said shut-off valve housing. Recent valves which represent these forms of gas shut-off devices are U.S. Pats. Nos. 4,373,548; 4,331,171; 4,336,818; 4,278,102 and 4,261,379. One exception to the shock or excess flow means of actuation is a recent Japanese shut-off valve (U.S. Pat. No. 4,043,350) which employs a pulled pin means to actuate a spring-biased closure mechanism.
The present invention is a marked improvement over the previous art, in that it not only reacts to the vibratory shock of a major earthquake, but also to a tilting moment and to an excess flow of gas caused by a sheared line within the gas distribution system. One excess flow device exists (U.S. Pat. No. 4,373,548), but does not react to the shock of a major earthquake.
Another important improvement over the prior art (U.S. Pat. No. 4,331,171; 4,336,818; 4,278,102 and 4,261,379) is that the present invention can be reset after actuation without partial disassembly, as is necessary with the inventions cited.
A final important feature of the present invention is that because of the valve's simplicity of design and limited number of moving parts, said invention can be manufactured and sold below the cost of the previous art, making it affordable to the general public.